Airbus Unveils A380 "Superjumbo" Jet

"The problem in analyzing the claims is that the companies make different underlying assumptions, particularly on the number of passengers the respective aircraft carry and the average flight length," said Kieran Daly, group editor with the publisher of Flight International magazine, in London.

Airbus envisions that airlines will use the ample space aboard the A380 for cocktail lounges and business conference rooms. That would reduce passenger capacity and cause the fuel consumption ratio to go up. Two of the A380 customers, Emirates Airlines and Singapore Airlines, both announced that they will configure their A380s with fewer than 500 seats.

"Imagine if you're flying a vast aircraft with half of the seats empty, the economicsand the emissions per passenger mile might look very different," said Simon Thomas, who heads Trucost, a London-based environmental research firm.

Rebuilding Airports

Airbus officials say increased demand and greater air congestion are driving the need for bigger planes.

"Traffic is doubling every 15 years, and airlines, airports and air traffic controllers have to find a way of facing up to this challenge," Velupillai said. "This challenge exists, whether the A380 exists or not."

Airbus envisions a network of international hubs that will ease congestion problems at major gateways.

Most of the large airports that will be served by the A380from Munich, Germany, to Bangkok, Thailandare already ready to handle the giant planes.

However, Los Angeles International Airport, which is expected to be one of the biggest hosts of A380 planes, is planning to build a new terminal for A380s. The bigger quarters would allow two A380s to park next to each other. If two A380 planes parked side-by-side in the biggest LA terminal today, their wings would hit each other.

So far, Airbus has sold 139 of the 280-million-U.S.-dollar A380s. Its largest customer is Emirates, a rapidly expanding state-owned carrier based in Dubai. No U.S. airlines have commissioned an A380, though Federal Express has ordered ten cargo versions of the plane.

A Fork in the Sky

While Airbus is banking on its giant plane, its main competitor, Boeing, is scheduling to debutin 2008its 7E7, a double-aisle aircraft aimed at the growing market for mid-size aircraft flown by low-fare carriers.

The two ventures illustrate the companies' opposing views of the future of commercial aviation, experts say.

So which future is more environmentally efficient?

The A380 will serve routes between large cities, using so-called megahubs. Many of those airports have a lot of congestion for takeoffs and landings, and the A380 is designed to solve that problem.

But Boeing believes passengers will prefer to fly smaller planes on services that connect more directly to destinations. Its 7E7 will be the lightest commercial airliner in the sky, Boeing claims, and the plane will be powered by the most efficient engines by far. These innovations, some experts say, more than compensate for the economies of scale that the A380 achieves.

"It would take less energy, and emit fewer pollutants, to fly several 7E7s from point A to point B than to put the same number of passengers on a single A380 for the trip," Durning said.

Smoggy Future

Whichever way the wind takes the airline industry, experts warn that the environmental challenges will only increase.

Airliners rate as one of the most polluting forms of transportation, with the world's 16,000 commercial jets producing over 600 million metric tons of carbon dioxide every year, according to one estimate.

The United Nations Intergovernmental Panel on Climate Change estimates that aviation causes 3.5 percent of man-made global warming, and that figure could rise to 15 percent by 2050.

Thomas, of Trucost, says technological improvements will help trim airline emissions by one percent a year. However, the aviation industry is forecasting 5 percent annual traffic growth worldwide for the next decades.

"Better technology alone is not going to solve this problem," he said.